There have been known certain numbers of carbostyril derivatives which exhibit useful pharmacological activities. For example, U.S. Pat. No. 4,070,470 and German Pat. (Laid-open) No. 2,527,937 teach carboxyalkoxy substituted carbostyril derivatives having blood platelet aggregation inhibitory effect; German Pat. (Laid-open) No. 2,825,048 teaches aminocarbonylalkoxycarbostyril derivatives having platelet aggregation inhibitory effect, phosphodiesterase inhibitory, effect, antiinflammatory effect, antiulcer effect and vasodilation effect. Further, U.S. Pat. No. 3,682,920 teaches 1-substituted derivatives of 3,4-dihydrocarbostyril which are useful as analgesic agents.
However, these carbostyril derivatives known in the prior art have some side effects, and which will cause some troubles in medical use.